1. Field of the Invention
This invention relates to feedthroughs for use in conjunction with packages for electrical components.
2. Brief Description of the Prior Art
Existing metal wall packages are very limited for low profile high, efficiency, high frequency packaging. No hermetic power package exists on the market today for high frequency (&gt;200 KHz) switch-mode power application.
The only hermetic power packages in production are constructed using metal walls with glass or ceramic feed-throughs with round metal leads. Packages such as TO-3, TO-254, TO-258 and multi-leaded hybrids of the same construction are extremely limited for today's high frequency, high efficiency and high density power requirements. The main limitations of standard glass to metal seals are:
1. Power loss due to high AC and DC lead resistance. (All glass seals require round Kovar or clad Kovar leads which have high electrical resistivity). Glass requires a thermal expansion matched material like Kovar to survive temperature extremes.
2. Eddy current loss due to the metal wall and metal leads. (eddy currents are induced in the metal wall around the sealed lead).
3. Round lead limitations at high frequencies. (Skin effect degrades the upper frequency limit).
4. Voltage breakdown and corona problems between leads and case due to the small glass seal diameters.
5. Weight problems with tall Kovar seal rings.